A long-felt need exists for a drug delivery system for remaining in the stomach over a prolonged period of time. The need exists for a drug delivery system that remains in the stomach and acts as an in vivo reservoir that releases drug at a controlled rate and continuously for (a) absorption in the stomach or for (b) passage into the intestine for absorption therein. Drug delivery systems are used clinically for administering a drug for its beneficial effect. Often the drug is administered from (1) a delivery system that releases a drug over time as the system moves through the gastrointestinal tract or from (2) a delivery system that remains in the stomach and releases drug while in the stomach. The delivery systems are used because they eliminate the need for administering a number of single doses at periodic intervals. The convenience of using a drug delivery system, which releases drug over a prolonged period of time as opposed to the administration of a number of doses, has long been recognized in the practice of medicine. The preferred sought-after therapeutic advantage to the patient and the clinician is controlled and optimum blood levels of drug during the period of time drug is released from the delivery system. This advantage arises from the delivery system continuously supplying drug for its passage and absorption into the blood for replacing drug used, eliminated, or metabolically inactivated by the patient.
The above presentation teaches that delivery systems have been provided for supplying continuously and for obtaining better therapy in the management of health and disease. For example, one system used for the continuous release of drug over a long period of time is disclosed by patentee Blythe in U.S. Pat. No. 2,738,303. The delivery system disclosed in this patent consists essentially of a capsule containing uncoated pellets of drug and coated pellets of drug having varying thickness. On their release from the capsule, the uncoated pellets provide an initial amount of drug and the coated pellets provide drug over a period of time. Another delivery system is disclosed by patentees Sheth et al in U.S. Pat. Nos. 4,140,775 and 4,167,558. The systems disclosed in these latter patents consists essentially of a tablet formed of a compressed polymer containing dispersed drug. The system is hydrodynamically balanced for remaining in the stomach for releasing drug therein over time.
While the above delivery systems are designed for providing a continuous supply of drug, there are inherent short-comings associated with these delivery systems. For example, pellets often pass through the gastrointestinal tract quickly, and this tends to limit the supplying of drug needed for maintaining a desired blood level of drug. Also, pellets are not designed for remaining in the stomach over an extended period of time as they tend to empty from the stomach in a first order manner like liquids. The tablet, on its exposure to stomach fluid, releases drug by uncontrolled leaching action and at a declining rate, which actions restrict the use of the tablet as a controlled delivery system during the time of its residency in the stomach.
In view of the above presentation, it will be appreciated by those versed in the drug dispensing art that if a delivery system is provided that remains in the stomach and acts as an in vivo drug reservoir while concurrently releasing drug in the stomach for (a) absorption in the stomach, or for (b) passage into the intestine for absorption therein, essentially without disrupting the normal emptying of ingested foods and liquids, such a delivery system would have a positive value and represent a substantial contribution to the dispensing art. Likewise, it will be appreciated by those skilled in the eart, that if a delivery system is made available that remains in the stomach for releasing drug at a controlled rate over time for achieving therapeutic blood levels, such a delivery system would be clinically useful in the practice of medicine.